Sex and love can be shared with more than one person. To be faithful is to be open & honest with a person as a parent can love more than one offspring. To love is to give, needing nothing in return.
Yes I have experienced both

100 % you can be in love with multiple people

You should consider one question at a time. Sex can be fun and mutually liberating but not spiritual. That would involve God and Thou probably doesn’t exist.

As long as you are honest and communicate well then it should be fine. It may be difficult but if you can do it and everyone wants to then I don't see why not.

Oops hit submit early anyway I generally like women that are creative generally musically as well as independent that can hold my interest inside and outside of the bedroom. Several of them have been bi and I’m pretty open to my friends needs whether that means sharing or simply giving them space when needed. I’ve even done a three way relationship but like I said that takes an open group of people but it is very possible!

It’s possible, but not probable.

That is theoretically possible, but difficult to manage and maintain. It would be an extraordinary relationship.

I think a person should ALWAYS be honest in their relationship(s).

When it comes to sex outside of marriage or a relationship, again, total honesty is the only way to make ti work. Whenever there is more than tow people involved in sex there will almost always be at least one person who feels at least left out. To expect any other result would just be unrealistic.

I have seen open relationships and nontraditional relationships work, but it required a great deal of honesty and laying out definite ground rules to which everyone willingly (as opposed to reluctantly) agrred to beforehand.

I knew a bisexual couple who agreed to be heterosexually monogamous to each other, but he would be free to have sex with men and she would be free to have sex with women. That would not work for everyone, but it worked well for hem.

Up until recently, many gay celebrities would marry "understanding" partners who were aware of their spouses homosexual affairs. Now that gays are becoming more widely accepted and gay marriage is legal in many countries, I expect gay celebrities will marry for love.

Few people are lucky enough to find someone who wants the same things when it comes to open relationships. The main problems are honesty and trust. Without those you get fear and jealousy.

Sex with friends almost always changes the friendship. To expect the friendship NOT to change would be unrealistic. We are animals with drives and instincts like all other animals. Our drives and instincts are expressed through sex and emotions. Unless you are a sociopath, it is nearly impossible to have sex with a person and not feel differently about them. (This would not hold for one night stands, or sex with virtual strangers, but only for people you actually know).

So, I think it is unlikely that sex, whether with friends or strangers, outside a relationship can enhance it, unless there is total and complete honesty. Even then, due to societal conditioning, it is not what most people would choose or want. Most experiments along these lines end in divorce, end the relationship or end a friendship.

It is the rare relationship where honesty and trust are strong enough to endure such experiments. Often, over time one person in the relationship will become attached to one of the "friends" more than they are to their partner. People are creatures of habit and seeing the same "riend" over and over would just be normal human behavior, so for long term happiness, I'd start working on developing honesty and trust with your partner before than look outside for "fun".

Developing honesty and trust will bring you closer and enhance your relationship far more than sexual adventures.